{an}是等差数列,bn={1/2}^an,已知b1+b2+b3=21/8,b1b2b3=1/8,证明{bn}是等比数列
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/23 13:41:06
![{an}是等差数列,bn={1/2}^an,已知b1+b2+b3=21/8,b1b2b3=1/8,证明{bn}是等比数列](/uploads/image/z/1761497-17-7.jpg?t=%7Ban%7D%E6%98%AF%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2Cbn%3D%7B1%2F2%7D%5Ean%2C%E5%B7%B2%E7%9F%A5b1%2Bb2%2Bb3%3D21%2F8%2Cb1b2b3%3D1%2F8%2C%E8%AF%81%E6%98%8E%7Bbn%7D%E6%98%AF%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97)
{an}是等差数列,bn={1/2}^an,已知b1+b2+b3=21/8,b1b2b3=1/8,证明{bn}是等比数列
{an}是等差数列,bn={1/2}^an,已知b1+b2+b3=21/8,b1b2b3=1/8,证明{bn}是等比数列
{an}是等差数列,bn={1/2}^an,已知b1+b2+b3=21/8,b1b2b3=1/8,证明{bn}是等比数列
bn=(1/2)^an bn-1=(1/2)^an-1
bn/bn-1=(1/2)^an-an-1=(1/2)^d是常数,
(d是{an}的公差
所以{bn}是等比数列